The place to test jq filters; useless for anything else.
On this page
Scores
Updated
Out of 5, from what each tool does. The reasons are in the reviews below.
Tool
Privacy
Features
Price
Aarrange
5
4
5
JSON Editor Online
4
4
4
jsonhero.io
3
2
5
JSONFormatter.org
1
3
5
JSONLint
1
2
5
Curious Concept
1
2
5
jqplay.org
1
2
5
What makes a great JSON formatter
JSON formatters seem simple: paste in messy JSON, get back pretty-printed output. But developers who use these tools daily know the difference between a bare-bones validator and something that actually fits into a workflow. A few traits separate the good ones from the rest.
Speed matters more than you'd expect. When you're debugging a 5,000-line API response at 11 PM, a tool that freezes or takes seconds to re-render is useless. The better formatters use modern editor engines like CodeMirror 6 or Monaco and handle large inputs without visible lag.
Validation quality varies a lot. Some tools only check whether the JSON parses. Others give you line-level error messages that actually help you fix the problem. A few go further with JSON Schema validation, letting you check structure and types against a defined schema, which is useful when you're building or consuming APIs.
Then there's what else the tool does: conversion (JSON to YAML, XML, CSV), minification, tree views, dark mode, keyboard shortcuts. These features add up. A tool that handles three tasks you'd otherwise need three bookmarks for saves real minutes across a workday.
The privacy factor
The most important difference on this list isn't a feature. It's an architecture decision: does the tool process your JSON in your browser, or does it send it to a server?
November 2025: saved snippets exposed on JSONFormatter.org and CodeBeautifyOn 25 November 2025, watchTowr Labs published research showing that JSON people had saved on JSONFormatter.org and CodeBeautify could be read by anyone. Both sites have a save-and-share feature and a public "Recent Links" page that lists saved entries. Using that page, the researchers downloaded more than 80,000 saved entries, about five years of JSONFormatter content and one year of CodeBeautify content, and found passwords, API keys, cloud and database credentials, Active Directory credentials and private keys among them. They also planted fake AWS keys as canary tokens, and someone tried to use one about 48 hours after upload, which suggests others were already scraping the sites. watchTowr did not describe it as a hack of the sites. The data was exposed through a feature that worked as designed.
The lesson reaches beyond one site. A server-side formatting tool is only as safe as the operator's infrastructure, logging practices and features like save and share. Client-side tools remove that risk: your JSON stays in your browser tab and never goes over the network.
In the comparison below, we flag each tool's processing model clearly. If you work with anything that could contain credentials, internal endpoints or customer data, this should be the first thing you check.
Detailed reviews
01
Aarrange
Everything runs in your browser; no jq or JMESPath queries.
100% client-side, so your data never leaves your browser
23 free tools in one place: JSON, YAML, TOML, CSV, XML, Markdown, HTML, CSS and SQL formatters, converters and more
JSON Schema validation (drafts 07, 2019-09 and 2020-12) and JSON to YAML/XML conversion built in
Errors show the exact line and column with a hint on how to fix them
No sign-up and no ads
Cons
Smaller community compared to legacy tools
No dark mode or themes
No jq or JMESPath queries
Aarrange gets the fundamentals right: fast formatting, real validation and zero data transmission. Every operation runs locally in JavaScript in your browser. You can verify this yourself by watching the Network tab in DevTools while using it.
The JSON Validator shows the exact line and column of an error with a hint on how to fix it, and it formats, minifies, sorts keys and shows the document as a tree. The JSON Schema Validator uses Ajv, supports drafts 07, 2019-09 and 2020-12, and can generate a schema or a sample document. Conversion to YAML and XML is built in.
Beyond JSON, Aarrange has 23 free tools in total, including formatters for YAML, TOML, CSV, XML, Markdown, HTML, CSS and SQL, so you don't need separate bookmarks for SQL formatting or YAML conversion. There is no sign-up and no ads.
The gaps are honest ones: it is a small site with a small community, it has no dark mode or themes, and it has no query language like jq or JMESPath.
JMESPath queries let you filter large JSON documents
Polished, modern interface
Cons
Advanced features require a paid plan
Performance drops on files larger than 10 MB
Paid tier syncs data through their servers
JSON Editor Online is the tool to reach for when you need to visually navigate nested structures. Code on the left, collapsible tree on the right. That dual-pane layout makes it easy to understand deeply nested objects without scrolling through raw text.
The free version handles everyday formatting and validation entirely in your browser. JMESPath support is genuinely useful if you work with large API responses and need to extract specific fields.
Here's the catch: power features like cloud storage and collaboration require upgrading, and the paid tier introduces server-side storage. For sensitive data, stick to the free version.
03
jsonhero.io
Great for exploring JSON; it can't format or edit.
Column-based navigation makes deep nesting manageable
Auto-detects and renders dates, URLs, images and colors inline
Open source on GitHub
Excellent for exploring unfamiliar API responses
Cons
Sharing feature uploads your data to their servers
No formatting or beautifying output. It's a viewer, not an editor
Can't edit or modify the JSON you're viewing
JSON Hero takes a different approach than traditional formatters. Instead of a text editor with pretty-printing, you get an explorer. The column view, inspired by Finder on macOS, lets you drill into nested objects without losing your place.
Automatic type detection is genuinely useful: dates get formatted, URLs become clickable links, and hex colors show a preview swatch.
The trade-off is that it's read-only. You can't format, edit or export modified JSON. And if you use the share feature, your data gets uploaded to their servers. For understanding what's inside a complex API response, few tools do it better. For actual formatting work, you'll need something else.
04
JSONFormatter.org
Plenty of features; your JSON goes to their server.
Feature-rich with formatting, validation and tree view
Includes JSON to XML and JSON to CSV converters
Large community and years of backlinks
Cons
Server-side processing, meaning your data is sent to their backend
Saved snippets were publicly exposed through its Recent Links page, as shown in November 2025
Heavy ad load slows down the experience
JSONFormatter.org built its reputation on being the first Google result for "json formatter" for years. Features are solid: formatting, validation, minification, tree view and basic conversion.
But November 2025 changed things. watchTowr Labs showed that JSON users had saved with the site's save feature was listed on a public "Recent Links" page, and collected more than 80,000 saved entries from JSONFormatter.org and CodeBeautify, including passwords, API keys and private keys. The researchers did not call it a hack: the feature worked as designed, and that was the problem.
The tool still works and the features are decent, but it sends your data to its backend. If you handle anything remotely sensitive, that's a hard trade-off to justify.
05
JSONLint
Clear error messages; little else, and it runs on a server.
Error messages pinpoint the exact line and character
Widely recognized and trusted name
Cons
All data is sent to their server
No indentation options, minification or conversion
Minimal feature set compared to modern alternatives
JSONLint has survived this long because it nails the basics. Paste JSON, click validate, and you immediately know if it's valid. When it's not, the error messages point to the exact line number and character position, which is usually enough to fix the problem on the first try.
That said, JSONLint sends your data to a server, ruling it out for anything containing secrets or personal data. It also lacks features beyond validation and basic formatting: no minification, no conversion, no themes, no tree view. It works well as a quick sanity check for public data, but it's not a daily-driver tool.
06
Curious Concept
Validates against specific RFCs; dated and server-side.
Configurable indentation (tabs or spaces, indent depth)
Running since 2007
Cons
Server-side processing, so data leaves your machine
Interface hasn't been meaningfully updated in years
No tree view, dark mode or conversion features
Curious Concept fills a narrow but useful niche: RFC-level validation. Most formatters validate against the current JSON spec and call it a day. Curious Concept lets you pick which RFC to validate against, whether that's RFC 4627 (the original), RFC 7159 or RFC 8259 (current). That matters when you're debugging compatibility issues with older parsers or strict enterprise systems.
Outside of that use case, it's a basic formatter with server-side processing and an interface that looks like it was last redesigned around 2012. Reliable for what it does, but not trying to be a general-purpose tool.
07
jqplay.org
The place to test jq filters; useless for anything else.
Server-side execution, so your JSON goes to their infrastructure
Useless if you don't need jq specifically
No formatting, validation or general-purpose features
jqplay is a specialist tool. If you're writing shell scripts that process JSON or just learning jq syntax, this saves you from installing jq locally just to test a filter. Type a jq expression, see the output update live, and share the result via URL.
The limitation is that jq runs as a native binary on their server, so your JSON input is sent over the network. Don't paste production credentials into it. It won't help with general-purpose JSON formatting. For testing jq filters specifically, though, it is the tool to use.
Search interest
How often people search Google for each tool by name, month by month over five years. It shows which names people know, not how many people use the tool. Google compares at most five names at a time, so this chart joins two searches that share JSON Editor Online.
Source: Google Trends, worldwide web search, Oct 2021 to Oct 2026 (Oct 2026 is a part month). This is search interest, not visits: 100 is the busiest month of any name in this chart, and the table shows averages. Fetched 2026-10-14.
Full feature comparison
This table maps every feature we evaluated across all seven tools: full support, partial or limited support, or no support.
Feature
Aarrange
JSON Editor Online
jsonhero.io
JSONFormatter.org
JSONLint
Curious Concept
jqplay.org
Core features
Format / beautify
Yes
Yes
No
Yes
Yes
Yes
No
Validate
Yes
Yes
No
Yes
Yes
Yes
No
Minify
Yes
Yes
No
Yes
No
No
No
Tree view
Yes
Yes
Yes
Yes
No
No
No
Conversion and advanced
JSON to YAML
Yes
No
No
Partly
No
No
No
JSON to XML
Yes
No
No
Partly
No
No
No
JSON Schema validation
Yes
Partly
No
No
No
No
No
jq filters
No
No
No
No
No
No
Yes
Editor and UX
Syntax highlighting
Yes
Yes
Yes
Yes
Partly
No
Yes
Dark mode
No
Yes
Yes
No
No
No
No
Customizable themes
No
Partly
No
No
No
No
No
Keyboard shortcuts
Yes
Yes
Partly
Partly
No
No
Partly
Privacy and security
Client-side processing
Yes
Yes
Partly
No
No
No
No
No data sent to server
Yes
Partly
No
No
No
No
No
Works offline
Partly
No
No
No
No
No
No
Additional
Multiple languages
Yes
No
No
Partly
No
No
No
Free (no limits)
Yes
Partly
Yes
Yes
Yes
Yes
Yes
How we tested
We evaluated each tool across five dimensions: core functionality (formatting, validation, minification), conversion capabilities, editor quality (syntax highlighting, themes, keyboard shortcuts), privacy architecture and general developer experience.
We tested each tool with payloads ranging from small config files (under 1 KB) to large API responses (50,000+ lines): a 200-line config file, a 5,000-line nested API response and a 50,000-line dataset. We measured time-to-format and noted any UI freezing or lag during input and rendering.
Privacy assessment was binary: we opened each tool's Network tab in Chrome DevTools, pasted JSON and performed every available operation. If any outbound request contained our submitted data, the tool was classified as server-side. Tools that only made requests for analytics or assets (not containing the user's JSON) were classified as client-side.
The scores on this page come only from that data: privacy from where the work happens, features from each tool's feature set compared with the others, and price from the pricing model. A tool with strong features but server-side processing scores lower on privacy than a client-side tool, whatever else it does.
DisclosureAarrange is our own tool. We built it because we wanted a JSON formatter that processed everything client-side and supported multiple languages in one interface. We've rated it on the same criteria as every other tool on this list, including its current limitations (no dark mode, no query language, smaller community). You're welcome to verify our claims. Open DevTools and check for yourself.
Our verdict
For most developers, Aarrange is the best overall pick. It handles formatting, validation, minification, schema validation, a tree view and conversion, all client-side and free with no feature gates, no account and no ads. If your work involves sensitive data, the privacy model alone puts it ahead. Try the JSON Validator.
Want a two-pane editor with a tree view and JMESPath queries? JSON Editor Online is the strongest option. Just stick to the free tier if privacy matters. For jq users, jqplay.org remains essential, though you should avoid pasting secrets.
After the 2025 exposure of saved snippets on JSONFormatter.org and CodeBeautify, picking a client-side tool just makes sense. Your JSON formatter should format JSON. It shouldn't publish your secrets.
FAQ
Is it safe to paste JSON into an online formatter?
It depends on where the tool processes your data. A client-side tool formats JSON in your browser and sends nothing over the network. A server-side tool sends your JSON to its backend, so it is only as safe as that operator's infrastructure, logging and features. Don't paste credentials, keys or customer data into a server-side tool.
What happened with JSONFormatter.org in November 2025?
watchTowr Labs showed that JSON users had saved on JSONFormatter.org and CodeBeautify was listed on a public "Recent Links" page. The researchers collected more than 80,000 saved entries containing passwords, API keys and other secrets. They did not describe it as a hack; the save-and-share feature exposed the data as designed.
How can I check whether a JSON formatter sends my data to a server?
Open the Network tab in your browser's DevTools, paste some JSON and use every button. If any outbound request contains your JSON, the tool processes it on a server. That is the test we used for every tool on this list.
Which JSON formatter has the best tree view?
JSON Editor Online, with code on one side and a collapsible tree on the other. jsonhero.io is the best pure explorer, with a column view and inline previews, but it can't format or edit.
Can I validate JSON against a JSON Schema online?
Yes. Aarrange's JSON Schema Validator runs Ajv in your browser and supports drafts 07, 2019-09 and 2020-12. JSON Editor Online has partial schema support. The other tools on this list don't validate against a schema.
How do I test a jq filter without installing jq?
Use jqplay.org. You type a jq expression and see the output update live. It runs jq on its server, so keep secrets out of the input.
Aarrange
JSON Editor Online
jsonhero.io
JSONFormatter.org
JSONLint
Curious Concept
jqplay.org
01
